基于CAD／CAPP并行设计的特征描述与操作

THE SCHEME OF DEFINING AND OPERATING FORM FEATURE FOR CAD/CAPP CONCURRENT DESIGNING

本文介绍了在作者开发的基于特征的ＣＡＤ／ＣＡＰＰ并行系统ＦＯＰＳ中，针对ＣＡＤ／ＣＡＰＰ并行设计的要求，对形状特征的表示处理策略。提出了基于加工的形状特征分类及体描述思想，并从一个新的角度认识处理形状特征，建立了基于特征描述的实体几何模型，提出了广义“凹孔”的特征认识概念及相应的“内环”处理技术，为有效地在设计过程中同时为ＣＡＰＰ系统提供必要的信息，便于进行零件设计的结构的工艺性分析、评价及工艺规程的自动生成，提供了一种实用的特征处理及操作技术。

o meet the needs of CAD/CAPP concurrent designing in Computer Aided Concurrent Engineering,a kind of representation scheme for defining and operating form feature based on manufacture is presented in this paper. With an extension concept of 'concave' for defining form feature , a method to represent form feature with 'inne rloops 'is introduced. Parts are then designed with true'Feature-Based Design'. The implementation of the physical data structure of B-rep solid model and form feature according to the representation scheme is presented and discussed. This scheme also provide enough message of part for CAPP system to analyze the manufacturability of parts and make the process planning automatically.